What brand of guitar do you have there? Here's what I used on a 631-mile canoe trip in May-June of this year - hand-made by my brother, all carbon-fiber.

Blacktop:

Nicknamed by my brother "Blacktop," this prototype 3-pound guitar was half-filled with rainwater many times in the 45 days of the trip and usually I could pour the water out the hollow neck, set it in the sun a few minutes, and it wouldn't even be out of tune! I now take it whenever I'm camping with the dogs in the sidecar (pic in my sig line).

He's planning to make these (now on his third design - this was the first) as one-off, custom instruments for people wanting a quality instrument that's unaffected by weather.

This is beyond cool. Does your brother have a price range in mind? Light, AND tough.. I have always just brought my harmonica because of those two demands... this would change things!